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Image quality evaluation method and apparatus thereof

a technology of image quality and evaluation method, which is applied in the direction of instruments, spectrometry/spectrophotometry/monochromators, optical radiation measurement, etc., can solve the problem that the correlation between the actual finished image and the evaluation result cannot be fully exploited

Inactive Publication Date: 2007-07-05
CANON KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0006] The first aspect of the present invention discloses a method of evaluating an image quality of printed matter of an image forming apparatus, the method comprising the steps of: outputting image data which forms an image with an arbitrary identical density within a range to be evaluated in one page to an image forming apparatus; inputting data of reflection characteristics of the image at a plurality of measurement points on an image surface of the printed matte

Problems solved by technology

Since the above evaluation method of homogeneity in page image does not consider such human visual perception characteristics, the correlation between the actually finished image and the evaluation result cannot be exploited fully.

Method used

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  • Image quality evaluation method and apparatus thereof
  • Image quality evaluation method and apparatus thereof

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Experimental program
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first embodiment

[Arrangement]

[0018]FIG. 1 is a block diagram showing the arrangement of a homogeneity in page image evaluation system of this embodiment.

[0019] An image quality evaluation program 11 installed in a personal computer (PC) 21 can read out evaluation data stored in storage media such as a hard disk drive (HDD) 22, and the like. The evaluation data include image data 12 as an evaluation chart, a measurement data set 13, and the like.

[0020] The measurement data set 13 includes spectral reflectance characteristics (absolute chromaticity and density) in a target and an image forming apparatus to be evaluated, device color information as signal values of a chart, patch position information, and the like as many as the number of patches.

[0021] In order to input the spectral reflectance characteristics of the evaluation chart, a spectrometer 23 is connected to an interface of the PC 21. The spectrometer 23 is desirably of an automatic scan type since the number of patches is large, but th...

second embodiment

[0036] The homogeneity in page image evaluation processing according to the second embodiment of the present invention will be described below. Note that the same reference numerals in the second embodiment denote the same parts as in the first embodiment, and a detailed description thereof will be omitted.

[0037]FIG. 4 is a flowchart for explaining the homogeneity in page image evaluation processing by the image quality evaluation program 11.

[0038] As in the first embodiment, the image quality evaluation program 11 outputs an image signal which has a signal level corresponding to an interest color and is required to form an image with a uniform density in the entire page to the image forming apparatus 25 which prints an output sample 26 (S31).

[0039] The program 11 then measures chromaticity values at a plurality of points in page image of the output sample 26 according to predetermined grid intervals, and stores the measured values in the memory such as the HDD 22 or the like (S3...

third embodiment

[0045] The homogeneity in page image evaluation processing according to the third embodiment of the present invention will be described below. Note that the same reference numerals in the third embodiment denote the same parts as in the first and second embodiments, and a detailed description thereof will be omitted.

[0046] The evaluation method of the above embodiments functions effectively when the heterogeneity in page image gradually becomes rich or pale in one direction. However, in case of periodic or local heterogeneity, the image quality evaluation program 11 may determine “pass” even for heterogeneity that one may actually find objectionable.

[0047] With this in mind, the program 11 shifts the reference point in the second embodiment in turn to grids A1, A2, A3, . . . , A10, B1, B2, . . . , N1, N2, . . . , N10 shown in FIG. 5. The program 11 calculates the distances λ and color differences ΔE between each reference point and all the measurement points, and calculates the ra...

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Abstract

Upon observing homogeneity in page image by the human eye, a permissible level associated with color reproduction with respect to an identical color signal changes depending on the distance from an interest point. Since the conventional homogeneity in page image evaluation scheme doesn't take the above characteristics into consideration, the correlation between a finished image and the evaluation result cannot be exploited fully. Hence, image data, which forms an image with identical density within a range to be evaluated in one page, is output to a printer to measure reflection characteristics of the image at points on output of the printer. One point is set as a reference point, and distances between the reference point and the remaining points, and differences of the reflection characteristic between the reference point and the remaining points are calculated. The image quality within the range is evaluated based on the distances and differences.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to evaluation processing for evaluating the image quality of printed matter of an image forming apparatus. [0003] 2. Description of the Related Art [0004] As one item for evaluating the image quality of printed matter, an evaluation scheme of homogeneity in page image associated with color reproductivity has been proposed. The evaluation scheme of homogeneity in page image evaluates color and density heterogeneities in one page image (to be referred to as heterogeneity in page image hereinafter, in other words, color differences in page image) using a small color difference spectrometer and XY stage. Therefore, an image based on image data of an identical density is formed on the entire page, the reflection characteristic value of the formed image is measured, and statistical values such as a maximum value, average value, standard deviation, and the like are acquired. Whether or not the...

Claims

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Application Information

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IPC IPC(8): H04N1/60
CPCH04N1/6094
Inventor SASANUMA, NOBUATSUITAGAKI, TOMOHISATOMITA, MASAMISAISHOJI, TOSHIOTAKAYAMA, SATOSHIHAYASHI, MIYOKO
Owner CANON KK
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